Original Sin - Preview @ Destructoid

As one might expect, the battles are no less strategic. Turn-based conflicts were decided upon in order to emphasize the need for strategy, and otherwise difficult fights can be made far easier with a little forward planning. One presented scenario involved a room with a giant skeletal robot, and healing shaman, a gang of skeleton warriors and suicide bombers. One player snuck around the group while the other shot an oil barrel with a fireball. The barrel exploded, causing the suicide bombers to blow up and take out half the opposition. Then he shot an electric bolt at a puddle near the skeletal robot, but the puddle was too small to reach it. Cue the second player, who cast a spell that made it rain, extending the reach of the puddle and bringing it to the enemy's foot, which was then stunned by the current running through the water.

Originally Posted by ToddMcF2002
So sorry for being late to this party but… Is all this awesomeness available in single player as a party based game? That would blow otherwise. All this multiplayer talk is a drag…

From Sven's Twitter

Yes, the game is very much intended to be played in single player, offline, but when you want up to 4 can play together.

So yeah, while having control of two guys is important, you can do it as single player if you want, you just control both guys. I think.